Electrical circuits are typically assembled by soldering active and passive electrical components onto solid boards. The components receive power and exchange signals by means of a network of conductive metal traces on one or both sides of the board. This approach to circuit fabrication, while virtually universal, nonetheless limits the manner in which electronic devices are housed and used. Generally, rigid boards are contained within an equally rigid cabinet, which sits on, or serves as, a piece of the user's furniture, or is instead mounted on an equipment rack. Indeed, the notion of electronics being packaged in "boxes" is so ubiquitous that alternatives are difficult to imagine.
But as the miniaturization of circuits continues, and as the range of materials from which electronic components may be formed expands, alternatives to traditional housings will assume increasing importance. In particular, much current research attempts to associate electronic circuitry more intimately with the user, so that its operation becomes a natural part of everyday action and routine. In this way, the user is spared the need to deliberately "operate" an external system, while the range of useful tasks amenable to electronic control or assistance is dramatically increased: environmental control, location monitoring, and exchange of information can all be effected without effort by the user or proximity to an external electronic device. In other words, by associating circuitry with the user rather than requiring the user to seek out the circuitry, the user need not interrupt or modify ordinary behavior to interact with electronics; instead, the electronics conforms to the behavior of the user.
Integrating electronic circuitry with clothing represents perhaps the most intimate (in the sense of proximity) and casual (in the sense of effortless availability) application of electronics to the everyday lives of individuals. While appealing, however, the idea of "wearable circuitry" remains elusive. People have long preferred the feel of woven cloth against the skin, conforming as it does to the human form and natural movements without discomfort. Directly integrating stiffly mounted electronic circuitry into traditional textiles would defeat their fundamental appeal.
Indeed, the characteristics of fabrics that render them ideal as clothing also offer advantages in numerous other applications. Fabrics can assume a wide variety of textures and appearances, as well as shapes and volumes; they are flexible, accommodate stress and movement without damage, and can be laundered. It is just these characteristics that traditional modalities for mounting electronic components lack.